Have had various tyre fitters do the balancing either with their adaptor cones or mine but have had better results by manually balancing them myself on the hub with the brake pads whipped out to let the wheel spin freely.
Also, having changed the tyres myself a couple of times I'll just continue to do it that way. Surprisingly easy to get them on and off, nothing like how difficult even a modern bike radial is, you don't even need a bead breaker to start the job.
